CD27, a TNF receptor family member was identified as a membrane molecule on human T cells (van Lier et al., 1987, J. Immunol. 139:1589-96). According to current evidence, CD27 has a single ligand, CD70, which is also a TNF family member (Goodwin et al., 1993, Cell 73:447-56).
CD27 is exclusively expressed by hematopoietic cells, in particular those of the lymphocyte lineage, i.e. T-, B- and NK cells. CD27 was originally defined as a human T-cell co-stimulatory molecule that increments the proliferative response to TCR stimulation (van Lier et al., 1987, J. Immunol. 139:1589-96). Presence of CD70, the ligand of CD27, dictates the timing and persistence of CD27-mediated co-stimulation.
Transgenic expression of CD70 in immature dendritic cells sufficed to convert immunological tolerance to virus or tumors into CD8+ T cell responsiveness. Likewise, agonistic soluble CD70 promoted the CD8+ T cell response upon such peptide immunization (Rowley et al., 2004, J Immunol 172:6039-6046) and in CD70 transgenic mice, CD4+ and CD8+ effector cell formation in response to TCR stimulation was greatly facilitated (Arens et al. 2001, Immunity 15:801-12; Tesselaar et al., 2003, Nat Immunol 4:49-54; Keller et al. 2008, Immunity 29: 334-346). In mouse lymphoma models, tumor rejection was improved upon CD70 transgenesis or injection of an anti-mouse CD27 antibody (Arens et al., 2003, J Exp Med 199:1595-1605; French et al., 2007, Blood 109: 4810-15; Sakanishi and Yagita, 2010, Biochem. Biophys. Res. Comm. 393: 829-835; WO 2008/051424; WO 2012/004367).
In WO2012/004367 the first anti-human agonistic antibody (designated hCD27.15) was described that does not require crosslinking to activate CD27-mediated co-stimulation of the immune response. In addition, an anti-human CD27 antibody, designated 1F5 was disclosed that activates CD27 upon crosslinking (WO2011/130434 and Vitale et al., Clin. Cancer Res, 2012, 18(14): 3812-3821). However, there is still a need in the art to develop anti-human CD27 antibodies having improved characteristics, including the ability to bind human CD27 having the A59T SNP and CD27 from cynomolgus monkeys.